Self-locking mechanism for a hot pluggable printed circuit board

ABSTRACT

A self-locking mechanism usable in conjunction with a printed circuit assembly (PCA). The self-locking mechanism generally comprises a central actuator, a pair of sliding members on either side of the actuator and one rotating lock member associated with each sliding member. The actuator, sliding members and rotating members preferably are mounted to a top edge of a vertically-mounted circuit board thereby forming the printed circuit assembly. The printed circuit assembly can only be removed from its host system after the actuator is turned to an unlocked position and then the sliding members are slid toward the actuator thereby causing the rotating lock members to disengage from their locked position. Turning the actuator also causes a signal to be asserted to the host system to disable power to the PCA. Upon installing the PCA, no power is provided to the PCA until it has been fully installed and the actuator locked.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to a provisional applicationentitled “Advanced Memory Protection,” Ser. No. 60/377,863, filed May 3,2002, and incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.

BACKGROUND OF THE INVENTION

[0003] 1. Field of the Invention

[0004] The present invention generally relates to a locking mechanismfor a printed circuit assembly (“PCA”). More particularly, the inventionrelates to a self-locking mechanism for a PCA and, more particularlystill, to a self-locking mechanism for a hot pluggable PCA that preventsa person from removing the PCA before the system in which the PCA isinstalled to have a chance to first power down the board.

[0005] 2. Background of the Invention

[0006] Computers and other types of electronic systems typically haveone or more circuit boards in addition to a system board. Each circuitincludes electronics and performs a desired function. Examples ofcircuit boards in a computer system include memory cards, sound cards,and graphics cards. Such boards are often referred to as printed circuitassemblies (“PCAs”) and that term is used in this disclosure to refer toany type or variation of circuit card usable in an electronic system.

[0007] More recently, “hot plug” PCAs and other devices have beenintroduced. A hot plug PCA is a circuit card that can be installed in,or removed from, a computer system while the computer system is poweredon and operational. Thus, if a PCA fails, that PCA can be removed and anew PCA installed without having to shut down and then reboot thesystem. Because powering down and rebooting the system is not necessarywith hot plug-capable PCAs, maintenance activities can occur much fasterwith much less of an impact on system operation. This is particularlybeneficial in mission critical systems (e.g., banks, Internet ServiceProviders) that can ill afford to have any down time.

[0008] Implementing a hot plug capability in a computer system is not atrivial task and generally requires addressing a number of issues. Forinstance, the host computer in general may store data or transmitcommands to the PCA. It is not desirable to disconnect the PCA from thecomputer while data is being written to the PCA. Otherwise, the data maybe lost. Also, it is not desirable to pull the PCA out of the system, orinsert it in the system while live voltages are being provided to thePCA. One way that this issue has been addressed to provide a switch inthe system that, when activated, powers down the PCA. Once powered down,the PCA then can be removed. The problem with this approach is thatnothing prevents a user from pulling out the PCA before activating theswitch. A better solution is needed.

BRIEF SUMMARY OF THE INVENTION

[0009] The problems noted above are solved in large part by aself-locking mechanism usable in conjunction with a printed circuitassembly. The self-locking mechanism generally comprises a centralactuator, a pair of sliding members on either side of the actuator andone rotating lock member associated with each sliding member. Theactuator, sliding members and rotating members preferably are mounted toa top edge of a vertically-mounted circuit board thereby forming theprinted circuit assembly.

[0010] In accordance with the preferred embodiment of the invention, theprinted circuit assembly cannot be removed from the electronic system inwhich it is mounted unless the self-locking mechanism is unlocked. Tounlock the mechanism, the central actuator is turned to an unlockedposition. The actuator includes a pair of cam surfaces which, while inthe locked position, engage corresponding surfaces of the slidingmembers thereby preventing the sliding members from being slid. Rotatingthe actuator to the unlocked position causes an electrical signal to beasserted to the electronic system so that the system can take whateversteps are necessary to disable communications to and power down theelectronics on the printed circuit assembly. Once the actuator is turnedto the unlocked position, the sliding members then can be slid towardthe actuator. The sliding members have non-flat (e.g., curved) tipportions which engage corresponding non-flat surfaces of the rotatinglock members. Sliding the sliding members causes the sliding members topush up on the rotating members thereby rotating the rotating memberstowards an unlocked position. The user can then grab the rotating lockmembers and pull up to remove the printed circuit assembly from itselectronic system. Further, upon installing the PCA into the system, nopower is provided to the PCA until the PCA has been fully installed andthe actuator turned to the locked position.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] For a detailed description of the preferred embodiments of theinvention, reference will now be made to the accompanying drawings inwhich:

[0012]FIG. 1 shows an isometric view preferred embodiment of aself-locking mechanism usable in conjunction with a printed circuitassembly (PCA);

[0013]FIG. 2 shows a top view of the self-locking mechanism in thelocked position;

[0014]FIG. 3 shows an isometric view of the self-locking mechanism inthe unlocked position;

[0015]FIG. 4 shows a back view of the self-locking mechanism in thelocked position;

[0016]FIG. 5 shows a back view of the self-locking mechanism in theunlocked position; and

[0017]FIG. 6 shows a top view of the self-locking mechanism in theunlocked position.

NOTATION AND NOMENCLATURE

[0018] Certain terms are used throughout the following description andclaims to refer to particular system components. As one skilled in theart will appreciate, computer companies may refer to a component bydifferent names. This document does not intend to distinguish betweencomponents that differ in name but not function. In the followingdiscussion and in the claims, the terms “including” and “comprising” areused in an open-ended fashion, and thus should be interpreted to mean“including, but not limited to . . . ”. Also, the term “couple” or“couples” is intended to mean either an indirect or direct electricalconnection. Thus, if a first device couples to a second device, thatconnection may be through a direct electrical connection, or through anindirect electrical connection via other devices and connections. Unlessotherwise stated, the term “hot plug” refers to installing and/orremoving an electronic device (e.g., a PCA) from an electronic system(e.g., a computer) while the system is powered on.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Referring now to FIG. 1, a printed circuit assembly (“PCA”) 40 isshown in accordance with a preferred embodiment of the invention. PCA 40generally includes a circuit board 42 on which electronic components 43are mounted. Such components 43 may include memory modules (e.g., dualin-line memory modules) and/or other types of components. The circuitboard 42 is preferably rectangular in shape, although the shape isgenerally irrelevant, and includes side edges 45 and a bottom edge 47 onwhich an edge electrical connector 51 is formed. The PCA 40 can beinstalled into an electronic system (e.g., a computer system such as aserver). The host system (not shown) in which the PCA is installedpreferably includes a pair of sliders that receive the circuit boardedges 45 as the PCA is moved in a downward vertical direction V. Assuch, the PCA is vertically mounted in its host system, although the PCAcan be readily configured for other mounting orientations. The edgeconnector 51 then mates with a corresponding electrical socket on a hostsystem board in the system thereby establishing electrical contactbetween the PCA 40 and its host system.

[0020] Referring still to FIG. 1, the PCA 40 also includes aself-locking mechanism 44 which includes a center locking actuator 46disposed between two side locking members 48. Self-locking mechanism 44is fixedly mated with a top surface of the circuit board 45 by screws orother types of fastener arrangements. Referring now to FIGS. 1, 2 and 3,the center locking actuator 46 comprises a gripping member 52 that auser can grip to thereby rotate the actuator between the locked positionshown in FIGS. 1 and 2 and an unlocked position as shown in FIG. 3. Theactuator 46 also includes a pair of cam surfaces 54. Each side lockingmembers 48 preferably comprise two pieces—a sliding member 56 and arotating lock member 60 (shown best in FIG. 3).

[0021] The sliding member 56 comprises a protruding portion 58 at theend nearest the locking actuator 46. The protruding portions 58 functionto contact cam surfaces 54 to prevent the sliding members 56 from movingfrom their locked position as shown in FIGS. 1 and 2. When lockingactuator 46 is rotated in a counter-clockwise direction to the openposition (FIG. 3), the cam surfaces 54 move out of the way of theprotruding portions 58 thereby permitting the sliding members 56 to bemoved along the horizontal H axis toward the locking actuator 46. Thisposition is also shown in FIG. 6 which illustrates that protrudingportions 58 of the sliding members 56 can move toward actuator 46without being impeded by cams 54. Although not specifically shown, thesliding members 56 include springs which operate to push the slidingmembers towards the outer edges 45 of the PCA thereby tending to keepthe mechanism 44 in a locked state. This horizontal sliding motion canbe performed by a person pushing finger contacts 64 in towards thelocking actuator 46. Finger contacts preferably include arrows 66indicating the direction of travel which are made from raised linesthereby increasing the gripability of the finger contacts 64 by aperson. Finger contacts may also include a vertically oriented fin 68 tofacilitate moving the sliding members 56 towards the center lockingactuator 46.

[0022] Referring now to FIG. 4, a back view of PCA 40 illustrates theinteraction between sliding member 56 and rotating lock member 60. Theouter portion of sliding member 56 includes a curved tip 72 as shownwhich generally presses against a correspondingly shaped surface 74formed in the underside of the rotating lock member 60. As the slidingmember 56 is moved laterally with respect to the rotating member 60, thecurved and raised tip 72 of the sliding member presses upward againstthe curved surface 74 thereby pressing upward on rotating lock member60. This upward pressure on the rotating members is large enough toovercome the friction force between the edge connector 51 and its matingsocket (not shown). As such, the rotating members 60 rotate as shown inFIG. 3 lifting the PCA enough so that the user can then grip therotating members 60 in finger portions 62 and pull the PCA all of theway out of the electronic system in which it was installed.

[0023] As is shown best in FIG. 4, rotating lock members 60 includelocking cams 75 formed or otherwise attached to their edges on theopposite side of rotation from rotation point 76. These locking cams 75contact corresponding surfaces in the electronic system in which PCA 40is installed to lock the PCA 40 in place. As shown in FIG. 5, rotatingthe lock members 60 upward causes the locking cam surfaces 75 to rotatedownward. The dimensions of the cams 75 are designed so that they moveinward enough when the lock members 60 are rotated upward to releasefrom their lock positions in the electronic system and permit the PCAcard to moved up and out of the system.

[0024] Installing the PCA 40 in its host system is generally the reverseof removing it as described above. With the rotating lock members 60 inthe generally open position (FIG. 3) and the center actuator 46 in theunlocked (FIG. 6), the PCA is slid into place into the system until theedge connector 51 generally touches the socket to which it is to mate.The user then pushes down on the rotating lock members 60. As therotating lock members 60 are pushed down toward their locked state andgenerally flush with the top surface of the self-locking mechanism 44,the curved tips 72 of the sliding members 56 engage their correspondingcurved surfaces 74 of the rotating lock members 60. The contact betweencurved tips 72 and surfaces 74 and the springs mentioned above tendingto push outward on the sliding members 60 cause the locking mechanism 44to effectively lock itself, hence the name “self-locking mechanism.”

[0025] The center actuator 46 also includes, or is coupled to,electrical conductors which assert a signal to electronics in the hostsystem when the actuator is turned from the locked to the unlockedposition, and vice versa. The signal informs the host system if the userdesires to remove the PCA or if the user has installed a PCA. If theuser is removing the PCA, the signal causes the host system to powerdown the PCA, so that the user can remove the PCA without damaging anyelectronics or causing data errors. If the user is installing the PCA,the signal causes the host system to enable power to the PCA and beginusing the PCA in accordance with its normal function (e.g., memoryboard).

[0026] Thus, as described the PCA includes a self-locking mechanism thatprevents a user from removing the PCA before the host system has had achance to cease data communications to the PCA and power it down. Themechanism also is easy to use to remove and install a PCA requiringrelatively little effort on the part of the user. The mechanism locksthe PCA in place as the PCA is mated with the host system by the user.Further, the mechanism advantageously requires no tools or loosefasteners to remove or install the PCA.

[0027] The above discussion is meant to be illustrative of theprinciples and various embodiments of the present invention. Numerousvariations and modifications will become apparent to those skilled inthe art once the above disclosure is fully appreciated. It is intendedthat the following claims be interpreted to embrace all such variationsand modifications.

What is claimed is:
 1. A locking mechanism for a printed circuitassembly PCA, comprising: a pair of sliding members; a central actuatordisposed between said sliding members capable of being turned by a user;and a pair of rotating lock members, one rotating lock member associatedwith each sliding member; wherein said sliding members, rotating lockmembers and central actuator are mated to a top edge of a PCA; andwherein the central actuator includes at least one cam surface which,unless moved out of the way by turning said actuator, contacts acorresponding surface of at least one of the sliding members therebypreventing said locking mechanism from being unlocked.
 2. The lockingmechanism of claim 1 wherein said central actuator includes two camsurfaces, each cam surface, unless said actuator is turned to anunlocked position, contacting a corresponding surface of a slidingmember thereby preventing said locking mechanism from being unlocked. 3.The locking mechanism of claim 1 wherein said central actuator causes asignal to be asserted to indicate that a hot plug event is about tooccur.
 4. The locking mechanism of claim 1 wherein each rotating lockmember is locked in place until said central actuator is turned and saidassociated sliding member is slid toward said central actuator.
 5. Thelocking member of claim 4 wherein each rotating lock member includes anon-flat surface and said associated sliding member includes a curvedtip portion which engages said non-flat surface, and said curved tipportion of said sliding member pushes upward on said non-flat surface ofsaid rotating member when said sliding member is slid toward saidcentral actuator thereby rotating said rotating member upward.
 6. Thelocking member of claim 5 wherein each rotating member includes alocking cam surface that functions to lock said PCA in place in anelectronic system in which said PCA is installed.
 7. The locking memberof claim 6 wherein said locking cam surfaces are rotated downward as therotating members are rotated upward.
 8. The locking member of claim 1wherein each rotating lock member includes a non-flat surface and saidassociated sliding member includes a curved tip portion which engagessaid non-flat surface, and said curved tip portion of said slidingmember pushes upward on said non-flat surface of said rotating memberwhen said sliding member is slid toward said central actuator therebyrotating said rotating member upward.
 9. The locking member of claim 8wherein each rotating member includes a locking cam surface thatfunctions to lock said PCA in place in an electronic system in whichsaid PCA is installed.
 10. The locking member of claim 9 wherein saidlocking cam surfaces are rotated downward as the rotating members arerotated upward.
 11. A printed circuit assembly (PCA), comprising: avertically-mounted circuit board having a top edge; and a self-lockingmechanism located on said top edge and locking said PCA in an electronicsystem and permitting said PCA to be removed from said system,comprising: a pair of sliding members; a central actuator disposedbetween said sliding members capable of being turned by a user; and apair of rotating lock members, one rotating lock member associated witheach sliding member; wherein said sliding members, rotating lock membersand central actuator are mated to a top edge of a PCA; and wherein thecentral actuator includes at least one cam surface which, unless movedout of the way by turning said actuator, contacts a correspondingsurface of at least one of the sliding members thereby preventing saidlocking mechanism from being unlocked.
 12. The PCA of claim 11 whereinsaid central actuator includes two cam surfaces, each cam surface,unless said actuator is turned to an unlocked position, contacting acorresponding surface of a sliding member thereby preventing saidlocking mechanism from being unlocked.
 13. The PCA of claim 11 whereinsaid central actuator causes a signal to be asserted to indicate that ahot plug event is about to occur.
 14. The PCA of claim 11 wherein eachrotating lock member is locked in place until said central actuator isturned and said associated sliding member is slid toward said centralactuator.
 15. The PCA of claim 14 wherein each rotating lock memberincludes a non-flat surface and said associated sliding member includesa curved tip portion which engages said non-flat surface, and saidcurved tip portion of said sliding member pushes upward on said non-flatsurface of said rotating member when said sliding member is slid towardsaid central actuator thereby rotating said rotating member upward. 16.The PCA of claim 15 wherein each rotating member includes a locking camsurface that functions to lock said PCA in place in an electronic systemin which said PCA is installed.
 17. The PCA of claim 16 wherein saidlocking cam surfaces are rotated downward as the rotating members arerotated upward.
 18. The PCA of claim 11 wherein each rotating lockmember includes a non-flat surface and said associated sliding memberincludes a curved tip portion which engages said non-flat surface, andsaid curved tip portion of said sliding member pushes upward on saidnon-flat surface of said rotating member when said sliding member isslid toward said central actuator thereby rotating said rotating memberupward.
 19. The PCA of claim 18 wherein each rotating member includes alocking cam surface that functions to lock said PCA in place in anelectronic system in which said PCA is installed.
 20. The PCA of claim19 wherein said locking cam surfaces are rotated downward as therotating members are rotated upward.
 21. A locking mechanism for aprinted circuit assembly PCA, comprising: a pair of sliding members; anda pair of rotating lock members having a point of rotation, one rotatinglock member associated with each sliding member and each rotating lockmember having a lever arm and a locking cam surface disposed aboutopposite sides of said rotation point; wherein said sliding members andsaid rotating lock members are mated to a top edge of the PCA; andwherein the locking cam surface of said rotating lock members engagecorresponding surfaces in an electronic system in which said PCA isinstalled; and wherein said sliding members must be slid to permit saidrotating lock members to be rotated about said point of rotation therebydisengaging said locking cam surfaces from their corresponding surfacesin the electronic system.
 22. The locking mechanism of claim 21 furtherincluding a central actuator disposed between said sliding members andcapable of being turned by a user.
 23. The locking mechanism of claim 22wherein the central actuator includes a pair of cam surfaces which,unless moved out of the way by turning said actuator, contacts acorresponding surface of at least one of the sliding members therebypreventing said sliding members from being slid.
 24. The locking memberof claim 21 wherein each rotating lock member includes a non-flatsurface and said associated sliding member includes a curved tip portionwhich engages said non-flat surface, and said curved tip portion of saidsliding member pushes upward on said non-flat surface of said rotatingmember when said sliding member is slid thereby rotating said rotatingmember upward.